I've searched and never found one clear and definitive answer for my question.

I'm drivin a 99Si and right now im basically doin the bolt-ons, i figure doin this will give me enough time to learn what i need to know and work on my car some to get the technical knowledge to try somethin harder down the road.

Anyway, i know the 4-2-1 is for emphasis on mid-range while the 4-1 is higher end. I've searched tons of forums and came to no definite answer, and it looks as if this forum is the most knowledagle so help me out... what would be the best choice? 421 or 41?

 

depends on the aplication... street/drag/1.6/1.8/2.0/2.0+

for a street B16 Id recomend a good 4-2-1

 

daily driven street driven b16a2, would probably never see a track unless i got some "real" work done.

 

For daily use on street 4-2-1 has better ground clearence for lowered cars...


but 4-1 should flow better

 

You SHOULD get better mid-range power from the 4-2-1 header and more top-end power from the 4-1. I have a 4-1 on my Si and feel like it gave me more mid-range power. It all depends on what you plan on doing to your car. Good Luck

 

I can't comment on how this swap would affect other blocks however I had a DC 4-2-1 and swapped out for the DC 4-1 and WOW what a difference. I gained 7 hp at peak but more impressive was my ELEVEN lb. ft. of torque at 4500 rpm. I found nothing but gains going to this header. This may be a result of having a port matched intake manifold and a p&p head on my B20vtec, but just looking at the tube diameter and bends the new header flows WAY better than my old one.

 

4-1

 

with this setup what should i run

b16 Dh-racing head Port and Poilsh
-ericking racing 68mm throttle body
-ib spec dual springs
-rev valves
-rev retainers
-jun 3 cams
-toda cam gears
-arp head bolts
-skunk 2 intake manifold
-j's racing intake with custom air ventalation to bumper
-Smsp header no cat to hks universal muffler

b18b1 block
-sleeving
-ib spec super doopers 86mm
-ls crank
-ib spec rods
-arp rod bolts
-z10 griddle
-custom oil pan
-itr tranny
-hasports hrydo to cable convo

 

cheap setup for you JDM 4-1 2.5' or ITR

otherwise look into hytech or an-r or other custom companies

 

Save up and get something custom.